JP2559724B2 - Power steering hydraulic control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a power steering, and more particularly to the hydraulic pressure of a power cylinder for steering front wheels to an actuator or a hydraulic sensor other than the power steering for steering front wheels. It is supplied, and these are operated according to the steering torque.

[Conventional technology]

Conventionally, as a hydraulic control device for power steering,
For example, the one described in JP-A-60-85061 is known.

In this conventional example, as an actuator other than the power steering for front wheel steering, an actuator of a rear wheel steering device is driven according to steering torque to perform four-wheel steering.

[Problems to be solved by the invention]

However, in the above-mentioned conventional hydraulic control system for power steering, a main pump dedicated to the power cylinder for front wheel steering and a sub pump dedicated to the power cylinder for rear wheel steering are provided in series on the output shaft of the engine, In addition, it is necessary to provide two types of hydraulic control valves for the front wheels and the rear wheels that respond to the steering torque of the steering wheel, which increases the engine horsepower consumed by both pumps and requires two piping systems and the hydraulic control valves. Since the number of gears is two, the configuration of the entire steering gear becomes large and it is difficult to mount it in the engine room of the vehicle. In addition, the steering gear, pump and piping are all dedicated products, resulting in increased manufacturing costs. There was a point.

In order to solve the above-mentioned problems, as disclosed in Japanese Patent Laid-Open No. 61-196876, a front wheel power cylinder and a rear wheel power cylinder, a pressure fluid is generated, and the pressure fluid is used as the front wheel power cylinder. And a fluid pump for supplying power to the rear wheel power cylinder, a fluid control valve for controlling the pressure fluid according to the steering of the steering wheel, and a power supply for the front wheel in the low speed range for the delivery of the pressure fluid from the fluid control valve. A four-wheel steering system has been proposed in which a cylinder includes a switching valve that switches to a power cylinder for rear wheels in a high speed range.

However, in this four-wheel steering system, although the fluid pump and the fluid control valve can be shared, a switching valve for switching the power cylinder for the front wheels and the power cylinder for the rear wheels according to the vehicle speed is required. As the number of points increases, the power cylinders for the front wheels are in operation at low speeds, the power cylinders for the rear wheels are in operation at high speeds, and only one of the power cylinders is in operation at any time. There is a new problem that both the front wheel steering and the rear wheel steering having different hydraulic characteristics cannot be reliably exhibited.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention configures a hydraulic bridge circuit by connecting four flow paths in a ring shape, and a front wheel steering power cylinder of a hydraulic cylinder circuit is provided between connection points on one diagonal line of the hydraulic bridge circuit. The left and right hydraulic chambers are connected, the other diagonal connection point is connected to a hydraulic pressure source, and an inflow control throttle that responds to the steering torque is provided in each flow path on the upstream side of the front wheel steering power cylinder. In a hydraulic control device for a power steering in which an outflow control throttle responding to the steering torque is provided in each flow path, at least one of the inflow control throttle and the outflow control throttle is provided on at least one of the upstream side and the downstream side, respectively. A first variable throttle that responds to the steering torque is inserted, and a steering wheel is arranged in parallel with the front wheel steering power cylinder between a connection point between the first variable throttle and another control throttle. An external control variable throttle in which the throttle area is controlled by an external signal other than C, forming a bypass flow path, and determining the differential pressure between both ends of the external control variable throttle as an actuator or hydraulic sensor other than the power cylinder for front wheel steering. The feature is that it is supplied to.

[Action]

According to the present invention, the first variable throttle is inserted in series with at least one of the inflow control throttle and the outflow control throttle provided in the hydraulic bridge circuit, and the first variable throttle and the inflow control throttle or the outflow control throttle in series with the first variable throttle are provided. A bypass flow path is provided between connection points of the external control variable throttles and the differential pressure generated at both ends of the external variable throttle is supplied to an actuator or hydraulic sensor other than the front wheel steering power cylinder. Therefore, when the external control variable throttle is fully opened, the differential pressure between the both ends becomes zero, and the actuator or the hydraulic sensor is deactivated.

On the other hand, when the external control throttle is fully closed, the differential pressure between both ends of the throttle is increased, and the actuator or the hydraulic sensor is activated.

Furthermore, if the external control throttle is selected to have an intermediate throttle area between fully closed and fully opened, it is possible to secure another actuator or hydraulic sensor in an intermediate operating state between them.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a hydraulic system diagram showing a first embodiment of the present invention.

In the figure, 10 is a hydraulic pump, 11 is a reservoir tank,
The hydraulic pump 10 and the reservoir tank 11 constitute a hydraulic pressure source.

A control valve 13 that controls a power cylinder 12 that generates a steering assist torque for a steering gear mechanism is interposed between the hydraulic pump 10 and the reservoir tank 11.

This control valve 13 has a hydraulic bridge circuit 14 in which _four flow paths L _{1 to} L ₄ are annularly connected, and one of the diagonal connection points C _A1 and C _A2 is connected to the hydraulic pump 10 and the reservoir tank 11. Connection points that are connected to each other and on the other diagonal
C _B1 and C _B2 are the left and right hydraulic chambers 12L and 1 of the power cylinder 12.
The hydraulic oil from the hydraulic pump 10 is connected to each of the 2Rs and corresponds to a steering operation to the right or to the left of the steering wheel 15, and a flow path L between the connection point C _A1 and the connection points C _B1 and C _{B2. 1} and L
It is configured to act with a pressure difference on the left and right hydraulic chambers 12L and 12R via ₂ .

Inflow control throttles 1L and 1R formed of variable orifices are inserted in the flow paths L ₁ and L ₂ , and outflow control throttles 2L formed of variable orifices are also formed in the flow paths L ₃ and L _4. , 2R is inserted. Then, the inflow control throttle 1 of the flow paths L ₁ and L ₂
First variable throttles 3R, 3L are inserted in series downstream of L, 1R, and a bypass passage L ₅ is provided between the first variable throttles 3R, 3L and the inflow control throttles 1L, 1R. An externally controlled variable throttle 5 constituted by an electromagnetic flow control throttle, which is communicated with the bypass flow path L ₅ and whose throttle area A ₅ is independently controlled according to the vehicle speed independently of the throttle, is inserted. Has been done.

The inflow control throttles 1L, 1R, the outflow control throttles 2L, 2R and the first
The variable throttles 3L, 3R are the inflow control throttle 1L and the outflow control throttle 2L by steering the steering wheel 15 to the left, for example.
And the first variable throttle 3L, the inflow control throttle 1R, the outflow control throttle 2R, and the first variable throttle 3R are steered to the right.
Are linked with each other and are configured to change in a direction in which the throttle area is reduced in accordance with a steering torque T described later. That is, based on the steering torque T due to the torsional elastic force of a torsion bar (not shown) or the like generated by the steering operation of the steering wheel 15, the respective apertures 1L, 1
The aperture areas A ₁ ; A ₂ and A _{3 of} R; 2L, 2R and 3L, 3R change.
Here, the throttle characteristics representing the relationship of the throttle area with respect to the steering torque T of each of the throttles 1L, 1R; 2L, 2R and 3L, 3R are respectively the second
The selections are made as shown in Figures (a), (b) and (c).

That is, as shown in FIG. 2 (a), each of the inflow control throttles 1L and 1R increases the steering torque T until the steering torque T reaches a predetermined value T ₁ , as indicated by a straight line l _11. decreases relatively steeply restriction area Te, exceeds a predetermined value T ₁ until the predetermined value T ₂ relatively slowly reduced as indicated by the straight line l _12, slightly above zero exceeds a predetermined value T ₂ It is selected to have a large aperture area.

Further, the outflow aperture control 2L, each of the 2R, as illustrated in FIG. 2 (b), until it reaches a predetermined value T ₁ is greater than a predetermined value T ₁ 'of the steering torque T, the inflow control throttle 1L, 1R are As shown by the straight line l ₂₁ , which is slightly more gradual than the direct l ₁₁ , the aperture area decreases relatively sharply, and the predetermined value T ₁ ′ to the predetermined value T ₂
Up to a larger predetermined value T ₂ ′, it decreases relatively gently as shown by a straight line l ₂₂ which is slightly gentler than the straight line l _12, and above a predetermined value T ₂ ′, the aperture slightly larger than zero. The area is selected.

Further, as shown in FIG. 2 (c), each of the first variable apertures 3L, 3R flows out until a predetermined value T ₁ ″ between the predetermined values T ₁ and T ₁ ′ of the steering torque T. It is selected so that the throttle area decreases relatively sharply as shown by the straight line l ₃₁ which is gentler than the straight line l ₂₁ of the control apertures 2L and 2R, and the aperture area becomes slightly larger than zero at the predetermined value T ₁ ″. ing.

Furthermore, the external control variable throttle 5, a vehicle speed detection signal V _D from the vehicle speed sensor 16 is supplied to the control unit U, the exciting current I _V having a current value corresponding to the value of the vehicle speed detection signal V _D at the control unit U is converted to, the excitation electromagnetic I _V is by supplying to the external control variable throttle 5, as shown in FIG. 2 (d) fully opened at the time of low vehicle speed, gradually restriction area with future increases in the vehicle speed It is selected for the throttle area characteristic that decreases and becomes fully closed at high vehicle speeds.

The differential pressure generated between both ends of the external control variable throttle 5 is supplied to the rear wheel steering power cylinder 18 for rear wheel steering.

In this rear wheel steering device 17, a driving force from an engine (not shown) is applied to a propeller shaft (not shown) differential gear device 19
And a rear wheel 22 which is transmitted via the rear axle 20 and is attached to, for example, a semi-trailing arm 21, which semi-trailing arm 21 is attached to a rear wheel member 23. The rear wheel member 23 is attached to a vehicle body (not shown) via a pin 24 and a rubber insulator 25, and a knuckle arm 26 is connected to a piston rod 18a of a rear wheel steering power cylinder 18 via a tie rod 27. Have. Reference numeral 28 is an elastic body such as a return spring and a rubber bush for maintaining the rear wheel 22 in the neutral position.

The specific configuration of the control valve 13 is the third
As shown in FIG. 6 to FIG. 6, the rotary valve 30 is used.

That is, in the valve housing 31, for example, a valve body 32 connected to a pinion of a rack and pinion type steering gear, and a cylindrical valve rotatably disposed on the inner peripheral surface thereof and connected to the steering wheel 15. The shaft 33 is provided with a torsion bar 34 which is disposed on the inner peripheral surface of the shaft 33 and has one end connected to the steering wheel 15 and the other end connected to a pinion of an ack-and-pinion type steering gear. And the rotary valve
Three sets of control valves 13 are formed in parallel with each other at an angle of 120 degrees.

Each control valve 13 has a valve body
Counter 32 and three oil grooves D ₁ to D _3, which is formed in and equiangular intervals extending axially on the inner peripheral surface of the oil groove D ₁ to D ₃ formed on the outer peripheral surface of the valve shaft 33 With ridges E _{1 to} E ₃
D ₁ and outlet aperture control 2L counterclockwise direction edge of the ridges E ₁ is the first variable throttle 3R in clockwise edge of the oil groove D ₁ and ridges E _1,
Inflow control throttle 1L at the counterclockwise edge of oil groove D ₂ and ridge E ₂
However, at the clockwise edge of the oil groove D ₂ and the ridge E ₂ , the inflow control throttle 1R
But first variable throttle 3L counterclockwise direction edges of the oil groove D ₃ and ridges E ₃ is, the outflow-side control aperture 2R are constituted respectively clockwise edge of the oil groove D ₃ and ridges E ₃ ing.

Then, the oil groove D ₂ of the valve body 32 is attached to the hydraulic pump 10,
The oil grooves F _{1 to} F ₃ of the valve shaft 33 are connected to the reservoir tank 11 via the oil passages and the through holes formed in the valve shaft 33, and the oil grooves D ₁ and D ₃ are the front wheel steering power cylinder 12. In the left pressure chamber 12L and the right pressure chamber 12R of the valve shaft 33, the oil grooves G _{1 to} G ₃ between the protrusions E ₁ and E ₂ of the valve shaft 33 and the protrusions E ₂ and
Oil groove H ₁ to H ₃ between E ₃ are respectively connected to the left pressure chamber 18L and the right pressure chamber 18R of the rear wheel steering power cylinder 18, and further,
An external control variable throttle 5 described later is connected between the oil grooves G _A and G _B. Here, the oil grooves F _{1 to} F ₃ , G _{1 to} G ₃ and H _{1 to} H ₃ formed on the outer peripheral surface of the valve shaft 33 are respectively shown in FIGS. 5 and 6 (a) and (b). As shown, the oil grooves F ₁ are formed by shifting the positions in the axial direction between the adjacent oil grooves.
~F _3, G ₁ ~G ₃ and H ₁ to H ₃ hydraulic oil inflow and Deana J ₁ through J ₅ formed in the valve body 32 communicating with is straight drilled radially.

On the other hand, in the valve housing 31, a spool valve 35 that forms the external control variable throttle 5 integrally with the rotary valve 30.
Are formed. This spool valve 35 is connected to an actuator 36a of an electromagnetic solenoid 36 and is slid by a spool 3
The external control variable throttle 5 has an oil groove K formed on the outer peripheral surface of the spool 37 and an oil groove M formed on the inner peripheral surface of the valve housing 31 facing the oil groove K.

The control valve 13 is not limited to the rotary valve 30 and may be a spool valve 40 as shown in FIGS. 7 and 8. That is, in the steering gear housing 41, the pinion shaft 42
A spool valve 40 is formed in a direction perpendicular to the spool valve 40, and a spool valve 42 constituting the external control variable throttle 5 is formed orthogonal to the spool valve 40.

The spool valve 40 has a spool 43 that slides in response to steering torque generated by steering of the steering wheel 15, and annular oil grooves P _{1 to} P ₄ are formed on the outer peripheral surface of the spool 43. On the other hand, the housing 41 facing the spool 43
Oil grooves Q _{1 to} Q ₃ that communicate with the oil grooves P _{1 to} P ₄ via a slight gap are formed on the inner peripheral surface of the. Here, the oil groove P ₃ and the communicating portion with the inflow control throttle 1R Q ₂ 'is, the oil groove P ₂ and Q ₂ of the communicating portion with the inflow control throttle 1L is first in communicating portion of the oil groove P ₂ and Q ₁ Variable throttle 3R is the first variable throttle 3L at the communicating portion of oil groove P ₃ and oil groove Q _3.
But the oil groove P ₄ and Q ₃ outflow aperture control 2R in communicating portion is, the oil groove P ₁
And Q _{1 form} the outflow control throttle 2L.

The oil groove Q ₂ is connected to the hydraulic pump 10 and the oil grooves P ₁ and P ₄ are connected to each other via the oil passage 46 formed in the spool 43 and connected to the reservoir tank 11, and the oil grooves Q ₁ and Q 4 are connected. _{3 in} the pressure chambers 12L and 12R of the power cylinder 12 for steering the front wheels, the oil groove P ₂ and
P ₃ is connected to the pressure chambers 18L and 18R of the rear wheel steering power cylinder 18 and to oil grooves K and M of the spool valve 42 described later, respectively.

The spool valve 42 has the same structure as the spool valve 35 in the rotary valve 30. Corresponding parts are designated by the same reference numerals and detailed description thereof will be omitted.

Next, the operation of the first embodiment will be described. Now, it is assumed that the vehicle is in the stopped state, the steering wheel 15 is not steered, and the front wheels and the rear wheels are in the neutral position in the straight traveling state. In this state, the throttle of the control valve 13
All of 1L, 1R to 3L, 3R are fully open, and the vehicle speed V detected by the vehicle speed sensor 16 is zero. Therefore, the external control variable throttle 5 is fully open, and the bypass passage The flow paths L ₁ and L ₂ are in communication with each other by L ₅ .

Therefore, the hydraulic oil of a predetermined hydraulic pressure supplied from the hydraulic pump 10 is entirely supplied to the hydraulic bridge circuit 14 of the control valve 13, and the flow paths L ₁ and L ₄ and the flow path L of the hydraulic bridge circuit 14 are supplied. _{Since the} flow is divided at a flow rate equal to ₂ and L ₃ , the left and right hydraulic chambers 12 of the front wheel steering power cylinder 12
Left and right hydraulic chambers 1 for L, 12R and power cylinder 18 for rear wheel steering
The 8L and 18R do not generate a pressure difference between the 8L and 18R, and the power cylinders 12 and 18 do not generate any steering assist torque, and the front wheels and the rear wheels maintain a straight traveling state.

In this stopped state, if the steering wheel 15 is turned to the right, for example, in a so-called stationary state, the throttles 1R to 3R are interlocked with each other in accordance with the steering torque at that time, and the throttle areas A _{1 to} A ₃ are in the reduction direction. However, the other diaphragms 1L to 3L maintain the fully opened state.

Therefore, a state in which the inflow control throttle 1L is not interposed for the channel L _1, Similarly, the flow path L ₂ first
Of the variable throttle 3L is a state that has not been inserted, also a state in which the outflow aperture control 2L is not inserted for passage L _4, the equivalent hydraulic circuit of the hydraulic bridge circuit 14 Fig. 9 (a)
It becomes as shown in.

Here, since the inflow control throttle 1R and the external control variable throttle 5 are in a parallel relationship, they can be regarded as a single equivalent variable throttle O _A that is the sum of the throttle areas A ₁ and A ₅ of both.
The equivalent hydraulic circuit of FIG. 9 (a) can be rewritten as shown in FIG. 9 (b).

Then, in FIG. 9 (b), the equivalent variable aperture O _A is
Since the throttle area A _A with respect to the steering torque T is sufficiently large, it can be regarded as a simple passage as shown in FIG. 9 (c).

In FIG. 9 (c), since the first variable throttle 3R and the outflow control throttle 2R are in a parallel relationship, these throttle areas are
A _3, A ₅ can be regarded as a single equivalent variable throttle O _B of summed equivalent throttle area _{A B (= A 3 + A} 5), as shown in FIG. 9 (d).

As is apparent from FIG. 9 (d), in the stationary state, high pressure hydraulic oil acts on both pressure chambers 18L and 18R of the rear wheel steering power cylinder 18, which results in a difference between the two. Since the pressure P _R is zero, the rear wheel steering power cylinder 18
Maintains the neutral state and does not generate steering force,
The front-wheel steering power cylinder 12, the presence of intervention interpolated equivalent variable throttle O _B in parallel thereto, as shown in FIG. 10, the hydraulic pressure supplied to the left pressure chamber 12L with the increase of the steering torque T Is increased and the steering torque T of a predetermined value T ₂ ′ or more is input, the maximum hydraulic pressure is supplied to the left pressure chamber 12L, and the right pressure chamber 12R becomes the drain pressure of the reservoir tank 11. Since P _F increases, the steering assist torque generated in the power cylinder 12 increases accordingly, and the steering operation of the steering wheel 15 can be performed lightly.

On the other hand, when the vehicle is traveling at a constant speed at a high speed, the vehicle speed sensor 16 outputs the high vehicle speed detection signal V _D, so that the control unit U outputs the exciting current I _V having a relatively high current value. Therefore, the diaphragm area A ₅ of the external control variable diaphragm ₅ is in a fully closed state. At this time, when the steering torque T is zero when the steering wheel 15 is not steered, each throttle of the control valve 13 maintains the fully open state as in the stationary operation, and both the power cylinders 12 and 18 are maintained. There is no pressure difference between the hydraulic chambers, and these power cylinders 1
No steering force is generated at 2,18.

However, if the steering wheel 15 is turned from the non-steered state to the right turning state, for example, as described above, the throttle areas of the throttles 1R to 3R of the control valve 13 are in the direction of reduction, and the throttles 1L to 3L. Keeps it fully open. Therefore, the equivalent hydraulic circuit of the hydraulic bridge circuit 14 is as shown in FIG. 11 (a).

Here, since the first variable throttle 3R is in the fully closed state due to a slight steering torque T, it is completely closed in the normal steering state and can be ignored. Therefore, the equivalent hydraulic pressure of FIG. The circuit can be rewritten as shown in FIG. 11 (b).

Therefore, as is clear from FIG. 11 (b),
In the inflow control throttle 1R and the outflow control throttle 2R, the throttle area of the former decreases with a smaller steering torque T than that of the latter, so that as shown in FIG.
In contrast, with a small steering torque, the left and right pressure chambers 18L, 18R
The differential pressure between the two
And the front wheel steering power cylinder 12 with respect to the front wheels, and with respect to the front wheel steering power cylinder 12, the difference between the left and right pressure chambers 12L, 12R is increased according to the throttle area characteristic of the outflow control throttle 2R as the steering torque T increases. The pressure will gradually increase, and the steering assist force generated in the front wheel steering power cylinder 12 will decrease.
The steering operation of the steering wheel 15 becomes heavy, and sudden steering can be prevented to improve steering stability.

Further, in a traveling state intermediate between the stationary state and the high speed traveling state, the differential pressure generated between the pressure chambers of the front wheel steering power cylinder 12 and the rear wheel steering power cylinder 18 is about the front wheel steering power cylinder 12. Decreases as the low-speed running state changes to the high-speed running state, and conversely increases for the rear-wheel steering power cylinder 18 as the low-speed running state changes to the high-speed running state. Both the front wheel steering and the rear wheel steering, which require different hydraulic characteristics with the power source and one hydraulic bridge circuit, can be reliably exhibited.

Next, a second embodiment of the present invention will be described with reference to FIG.

In the second embodiment, in the configuration of the first embodiment, the first variable throttles 3R, 3L provided on the upstream side of the power cylinder 12 of the hydraulic bridge circuit 14 are replaced by the power cylinder 12
Is arranged in series with the outflow control throttles 2L, 2R on the downstream side, and the first variable throttles 3R, 3L are disposed on the upstream side, and the inflow control throttles 1L,
The throttle area characteristic of 1R and the throttle area characteristics of the outflow control throttles 2L and 2R are replaced with each other, and further, the connection point of the first variable throttle 3L and the outflow control throttle 2R and the first variable throttle 3R and the outflow control throttle
Except that communicates a bypass channel L ₅ with interposed the external control variable throttle 5 between the connection point of the 2L has a configuration similar to the above first embodiment, correspondence between the first FIG. The same reference numerals are given to the parts, and the detailed description thereof will be omitted.

According to the second embodiment, when the steering wheel 15 is turned to the right, the equivalent circuit of the hydraulic bridge circuit 14 is, as shown in FIG. 14, the first circuit shown in FIG. 9 (a) in the first embodiment. The upstream side and the downstream side of the other parts except the variable throttles 3L and 3R are reversed. However, as in the first embodiment, the outflow control throttle 3R and the external control variable throttle 5 are parallel to each other. a relationship, and since the restriction area a ₅ of the external control variable throttle 5 is large, they can be considered as a mere oil passage, thus the result shown in FIG. 15 corresponding to FIG. 10 (d) As described above, the rear wheel steering power cylinder 18 is bypassed, and the throttle area A ₂ of the first variable throttle 2R and the throttle area A ₃ of the first variable throttle 3R are arranged in parallel with the steering power cylinder 12. By inserting the equivalent variable aperture O _C of the equivalent aperture area A _C represented by In the front wheel steering power cylinder 12, the same differential pressure characteristic with respect to the steering torque as in the first embodiment can be obtained.

Similarly, during high-speed running, the front wheel steering power cylinder 12 and the rear wheel steering power cylinder 18 connected in series are connected in parallel to the inflow control throttle 1R and the outflow control throttle 2R, respectively. A differential pressure that gradually increases with increasing steering torque is generated in the steering power cylinder 12, and a differential pressure that sharply increases with increasing steering torque is generated in the rear wheel steering power cylinder 18. It is possible to generate the steering assist torque for the front wheels and the steering force for the rear wheels as in the first embodiment.

Similarly, even in the intermediate running state during stationary running and high-speed running, the front wheel steering power cylinder 12 and the rear wheel steering power cylinder 18 can generate steering assist force and steering force exactly the same as in the first embodiment. it can.

Next, a third embodiment of the present invention will be described with reference to FIG.

In the third embodiment, the rear wheel steering device 17 in the first embodiment is fixed to the left and right rubber insulators 25 of the rear wheel member 23, instead of the rear wheel steering power cylinder 18, to the vehicle body side member. Rear wheel steering power cylinder 51L,
The piston rod 51a of the 51R is connected, and the pressure chamber 51b of the power cylinder 51L and the pressure chamber 51c of the power cylinder 51R are connected by a hydraulic pipe 52, and the pressure chamber 51c of the power cylinder 51L and the pressure of the power cylinder 51R are connected. The chamber 51b communicates with the hydraulic pipe 53, and the pressure chamber 51b of the power cylinder 51L is connected to the external control variable throttle 5 and the flow path L ₁ and the pressure chamber 51b of the power cylinder 51R is variable by the external control. It has the same structure as that of the first embodiment except that it is connected to the connection points of the throttle 5 and the flow path L ₂ , respectively, and the corresponding parts to those in FIG. The detailed description is omitted here.

Also in this third embodiment, the left and right rubber insulators 24 are pressed in opposite phases by the rear wheel steering power cylinders 51L and 51R, and the rear wheel member 23 is slightly tilted. Rear wheel
Since it has the same configuration as that of the first embodiment except that the steering wheel 22 is steered in phase with the front wheels, it is possible to obtain the same effect as that of the first embodiment.

Next, a fourth embodiment of the present invention will be described with reference to FIG.

In the fourth embodiment, the bypass flow path L _{6 in} which the external control variable throttle 6 is inserted is connected in parallel with the front wheel steering power cylinder 12 in the first embodiment, and the throttle of the external control throttle ₆ is connected. It has the same structure as that of FIG. 1 except that the area characteristics are selected so as to sequentially increase as the vehicle speed increases, as shown in FIG. Are denoted by the same reference numerals and detailed description thereof will be omitted.

According to the fourth embodiment, the external control variable throttle 6 inserted in parallel with the front-wheel steering power cylinder 12 is installed in the stationary steering state in which the steering wheel 15 is turned to the right, for example, when the vehicle speed is low or at a low vehicle speed in the vicinity thereof. Since it is in a fully closed state as shown in FIG. 18, its equivalent circuit is exactly the same as that in FIG. 10 (a), and therefore a large differential pressure is applied to the front wheel steering power cylinder 12 just as in the first embodiment. Is supplied to the front wheel steering power cylinder 12, a large steering assist force can be generated.

On the other hand, when traveling at high vehicle speeds, the power cylinder for steering the front wheels
Aperture area A ₆ of external control variable aperture 6 inserted in parallel with 12
Is in the open state in which the predetermined value A _S is maintained, and its equivalent circuit is as shown in FIG. 19 (a).

In this Fig. 19 (a), since the outflow aperture control 2R and the external control diaphragm 6 becomes parallel relationship, when these are substituted into one equivalent variable throttle O _D, the as shown in Figure 19 (b) restriction area a _D is represented by the sum of the restriction area a ₆ of the throttle area a ₂ and the external control variable throttle 6 of the outflow throttle control 2R. Therefore,
Since the throttle area A _C of the equivalent variable throttle O _D has a sufficiently large area, it can be considered as a mere oil passage, and therefore, the equivalent variable throttle O _D allows the pressure chambers 12L on the left and right sides of the steering power cylinder 12 to be As 12R is bypassed,
As shown in FIG. 20, the pressure difference between the pressure chambers 12L and 12R becomes substantially zero, which is equal to the manual steering state.

On the other hand, in the rear wheel steering power cylinder 18, since the inflow control throttle 1R is inserted in parallel with the power cylinder 18, the differential pressure between the pressure chambers 18L, 18R depends on the throttle area characteristic of the inflow control throttle 1R. As the steering torque increases, the steering torque rapidly increases, and a large rear-wheel steering force can be generated by the rear-wheel steering power cylinder 18.

Further, in an intermediate traveling state during stationary operation and high-speed traveling, the steering assist force and steering force intermediate between the two can be generated by the front wheel steering power cylinder 12 and the rear wheel steering power cylinder 18.

Next, a fifth embodiment of the present invention will be described with reference to FIG.

In the fifth embodiment, in the first embodiment, the flow path L ₃ on the downstream side of the front wheel steering power cylinder 12 and
Downstream of the outlet aperture control 2R and 2L in L _4, which a second variable throttle 4R and 4L are inserted in series, and squeezed between the connection point of the connection point with the diaphragm 2L and 4L of 2R and 4R A bypass flow path L ₆ is formed in the bypass flow path L _6, and the external control variable throttle 6 is inserted in the bypass flow path L ₆ and has the same configuration as that of the first embodiment. Corresponding parts are designated by the same reference numerals, and detailed description thereof will be omitted. Here, the throttle area characteristics of the outflow control throttles 2L and 2R are, as shown in FIG. 22 (a), compared to the throttle area characteristics of the outflow control throttles 2L and 2R in FIG. As shown in FIG. 22 (b), the diaphragm area characteristics of the second variable diaphragms 4L and 4R are selected so as to be relatively gentle so as to be large.
The outflow control throttles 2L and 2R shown in FIG. 1 are selected to have the same throttle area characteristics, and the external control variable throttle 6 has the same throttle area characteristics as shown in FIG. 18 (b) as in the case of the fourth embodiment. The throttle area is selected so as to increase as the vehicle speed V increases.

According to the fifth embodiment, the external control variable throttle 6 is in the fully closed state when the steering wheel 15 is stationary, for example, to the right when the vehicle speed is low or when the vehicle speed is low and the bypass flow path L ₆ Is in the cutoff state, and therefore, in the flow path L ₃ , the outflow control throttle 2R and the second variable throttle
It means that 4R and 4R are inserted in series. Therefore, if these two diaphragms 2R and 4R are regarded as a single equivalent variable diaphragm O _E , the diaphragm area A _E can be expressed by the following equation.

Here, since the outflow control throttle 2R and the second variable throttle 4R are selected so that the throttle area A ₄ of the second variable throttle 4R is smaller than the same steering torque, the throttle in the flow path L ₃ is reduced. The area is dominated by the throttle area of the second variable throttle 4R and is substantially equal to the outflow control throttle 2R in the first embodiment. Therefore, a large steering assist force substantially similar to that at the time of stationary operation in the first embodiment is applied to the front wheel steering power cylinder 12.
Can be generated from.

Further, at the time of high speed running, restriction area A ₆ of the external control variable aperture 6, as shown in the FIG. 19, since a diaphragm area of a predetermined value, in the flow path L _3, stop the second variable 4R and the external control variable throttle 6 becomes parallel relationship, when both regarded as a single equivalent variable throttle O _F, the aperture area a _F is squeezed second variable throttle aperture area a ₄ of 4R and the external control variable 6 is represented by the sum of the restriction area a ₆ of because its aperture area is sufficiently large, it is possible to the equivalent throttle O _F regarded as merely an oil passage,
Therefore it it is equivalent that inserted simply outflow aperture control 2R Nomigakai the flow path L _3, it is possible to generate a small steering assist force exactly the same as the first embodiment from the front-wheel steering force power cylinder 12 At the same time, a large rear wheel steering force can be generated from the rear wheel steering power cylinder 18.

In this fifth embodiment, to omit the bypass passage L _6, each of the first variable throttle 4L Alternatively, each to form a bypass flow path in parallel with the 4R, respectively external control for these bypass channel Even if the variable diaphragm 6 is inserted, the same effect as the above can be obtained.

Instead of providing the external variable throttle 6 in the fourth and fifth embodiments, the steering force of the front wheel steering power steering may be controlled by the vehicle speed or the like by known reaction force control.

Next, a sixth embodiment of the present invention will be described with reference to FIG.

This sixth embodiment is the same as the third embodiment except that hydraulic piping is used.
Without using 52 and 53, the hydraulic chamber 51C of the power cylinder 51R and the hydraulic chamber 5 of the power cylinder 51L connected to the hydraulic pump 10 side
It has the same configuration as that of the third embodiment except that 1C is connected by a hydraulic pipe 63, and the same action and effect can be obtained.

In the first to sixth embodiments, the case where the rear wheel steering power cylinder is applied as the actuator that uses the surplus hydraulic pressure of the front wheel steering power cylinder 12 has been described, but the present invention is not limited to this. Alternatively, the surplus hydraulic pressure may be supplied to another vehicle-mounted actuator, or the surplus hydraulic pressure may be supplied to the pressure sensor to monitor the operating state of the front wheel steering power cylinder 12, and to detect the pressure sensor detection signal. Based on front wheel steering power cylinder 12
It can also be used for diagnosing an abnormal condition of the power cylinder. In this case, a smaller pressure can be derived compared to the one that directly guides the pressure applied to the power cylinder, so the pressure sensor can also be downsized, and the power steering for the front wheel steering is also possible. Since it is possible to create a linear hydraulic pressure characteristic, unlike the hydraulic pressure characteristic of, it can be used as a steering torque sensor and can also actuate other actuators.

Further, in the above-mentioned first to sixth embodiments, the case where the external control variable throttles 5 and 6 are controlled according to the vehicle speed has been described, but the present invention is not limited to this, and as shown in FIG. The vehicle speed detection signal V _D of the vehicle speed sensor 16 is sent to the control unit U.
Instead of the above, a selection signal of a steering torque selector 60 including a rotary switch, a variable resistor, etc. provided near the driver's seat is supplied, and the steering torque selector 60 is operated to output from the control unit U. The value of the exciting current I _V to be changed can be arbitrarily changed, the equivalent throttle area A of the entire hydraulic bridge circuit 14 is arbitrarily changed according to the driver's preference, and an arbitrary steering torque is changed to the power cylinders 12, 18 You may make it generate | occur | produce by.

Further, as shown in FIG. 25, a friction coefficient sensor 61 for detecting the friction coefficient of the road surface is provided, and by changing the exciting current from the control unit U according to the friction coefficient detection value of the friction coefficient sensor 61, The optimum steering torque may be generated according to the friction coefficient of the road surface. That is, the detected friction coefficient value from the friction coefficient sensor 61 is the control unit U.
The control unit U controls the value of the exciting current _{IV to} a relatively small value when the friction coefficient is low, to a large value when the friction coefficient is high, and to an intermediate value between the two when the friction coefficient is intermediate. . Here, as the friction coefficient sensor 61, a changeover switch that interlocks with a wiper switch, a raindrop sensor or the like that indirectly detects the road surface friction coefficient, or the rotational speeds of the front and rear wheels of the vehicle are detected, and the rotation of both is detected. For example, a friction coefficient may be calculated by calculating the number difference, or a friction coefficient may be calculated by detecting the splash amount of the drive wheels, or the like, which directly detects the road friction coefficient. In this case, the excitation current value calculated according to the vehicle speed may be corrected by the friction coefficient detection value of the friction coefficient sensor 61 without being limited to the case where the external control variable throttles 5, 6 are controlled only by the road surface friction coefficient.

In addition, a sensor that detects the operation of the vehicle's acceleration / deceleration device is provided, and the frequency of acceleration / deceleration of the vehicle is calculated based on the detection value of this sensor. When the vehicle speed is controlled by the vehicle speed, the vehicle speed sensitive pattern, that is, the throttle area characteristic with respect to the vehicle speed in FIGS. 2 (d) and 18 may be changed.
A steering angle sensor for detecting the steering angle of the steering wheel 15 and a steering angular velocity calculation means for differentiating the output to calculate the steering angular velocity are provided, and the steering angle detection value of the steering angle sensor and the steering angular velocity calculation value of the steering angular velocity calculation means are provided. Based on the above, the vehicle speed response pattern may be changed to prevent sudden steering to improve steering stability. Further, a load sensor for detecting the front wheel load of the vehicle is provided, and an external sensor is provided according to the change of the front wheel load. The controllable diaphragms 5 and 6 may be controlled.

Further, in the first to sixth embodiments, the case where the rack and pinion type is applied as the steering gear mechanism has been described, but the present invention is not limited to this, and other types of steering gear mechanisms may be applied. Needless to say.

〔The invention's effect〕

As described above, according to the present invention, the operating hydraulic pressure supplied to the front-wheel steering power cylinder by one hydraulic bridge circuit has the necessary hydraulic characteristics as in the front-wheel steering power cylinder as in the rear-wheel steering power cylinder. It can also be supplied to other actuators or hydraulic pressure sensors different from those used to operate them simultaneously with the power cylinder for steering the front wheels, which does not increase the overall size, reduces manufacturing costs, and allows switching. Since no valve is required, the number of parts can be reduced, and the reliability of long-term use can be improved.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing a first embodiment of a power steering hydraulic control device according to the present invention, and FIG.
(D) is an inflow control throttle applicable to the present invention,
A characteristic diagram showing throttle area characteristics of the outflow control throttle, the first variable throttle, and the external control variable throttle, FIG. 3 is a sectional view showing an example of a rotary valve applicable to the present invention, and FIG.
Sectional drawing on the BB line of a figure, FIG. 5 is a perspective view which shows an example of a valve shaft, FIG.6 (a) and (b) are the developed views of a valve shaft and a valve body, respectively, and its VII-V.
A sectional view taken along the line II, FIG. 7 is a sectional view showing an example of a spool valve applicable to the present invention, and FIG. 8 is a VIII- of FIG.
A sectional view on the line VIII, FIGS. 9 (a) to 9 (d) are explanatory views for explaining the operation in the stationary state of the first embodiment, and FIG. 10 is a characteristic showing hydraulic characteristics with respect to steering torque in the stationary state. The diagrams and FIGS. 11 (a) to 11 (c) are explanatory views for explaining the operation at the time of right-turning in the high-speed traveling state of the first embodiment, respectively.
FIG. 12 is a characteristic diagram showing hydraulic pressure characteristics with respect to steering torque during high-speed traveling, FIG. 13 is a hydraulic circuit diagram showing a second embodiment of the present invention, and FIGS. 14 and 15 are installation diagrams of the second embodiment. FIG. 16 is a hydraulic circuit diagram showing a third embodiment of the present invention, FIG. 17 is a hydraulic circuit diagram showing a fourth embodiment of the present invention, and FIG. A characteristic diagram showing the throttle area characteristics with respect to the steering torque of the external control variable throttle 6 in the embodiment, and FIGS.
Explanatory drawing for explaining the operation at the time of stationary operation in the embodiment,
FIG. 20 is a characteristic diagram showing a hydraulic characteristic with respect to steering torque when turning to the right in a high speed traveling state in a fourth embodiment, FIG. 21 is a hydraulic circuit diagram showing a fifth embodiment of the present invention, and FIG. )
And (b) are characteristic line diagrams showing throttle area characteristics with respect to steering torque of the outflow control throttle and the second variable throttle in the fifth embodiment, respectively, and FIG. 23 is a hydraulic circuit diagram showing the sixth embodiment of the present invention. 24 and 25 are hydraulic circuit diagrams showing other embodiments of the present invention. In the figure, 1L and 1R are inflow control throttles, 2L and 2R are outflow control throttles, 3
L and 3R are first variable throttles, 4L and 4R are second variable throttles, 5 and 6 are externally controlled variable throttles, 10 is a hydraulic pump, 11 is a reservoir tank, 12 is a front wheel steering power cylinder, and 12L and 12R Is a hydraulic chamber, 13 is a control valve, 14 is a hydraulic bridge circuit,
L _{1 to} L ₄ are flow paths, L ₅ is a bypass flow path, 15 is a steering wheel, 16 is a vehicle speed sensor, U is a control unit, 17 is a rear wheel steering device, 18 is a rear wheel steering power cylinder, and 18L, 18R Is a hydraulic chamber, 30 is a rotary valve, 40 is a spool valve, 60
Is a steering torque selector, and 61 is a friction coefficient sensor.

Claims (1)

(57) [Claims] 1. A hydraulic bridge circuit is formed by connecting four flow paths in an annular shape, and the left and right hydraulic chambers of a front wheel steering power cylinder are connected between connection points on one diagonal line of the hydraulic bridge circuit. The other diagonal connection point is connected to a hydraulic pressure source, and an inflow control throttle that responds to steering torque is provided in each of the upstream passages of the front wheel steering power cylinder, and the steering torque is provided in each of the downstream passages. In a hydraulic pressure control device for a power steering, each of which is provided with an outflow control throttle in response to the first control valve, in response to a steering torque, at least one of an upstream side and a downstream side of at least one of the inflow control throttles and the outflow control throttles responds to a steering torque. Of the variable throttle is inserted between the first variable throttle and another control throttle in parallel with the front wheel steering power cylinder by an external signal other than the steering torque. By forming a bypass passage through which an external control variable throttle whose area is controlled is inserted, the differential pressure between both ends of the external control variable throttle is supplied to an actuator or a hydraulic sensor other than the front wheel steering power cylinder. A hydraulic control device for a power steering, which is characterized in that